how do fossils form?

Question

it's for my science and if you can, write it in french

Answer 1

There are several ways fossils form. One easy to understand way is to consider a leaf impression. If the leaf impression in mud gets covered over by more mud, and then gets buried deeply (thousands of feet), over time the mud may become the sedimentary rock called shale, and if exposed to the surface again the leaf impression can be found by splitting the rock at the right spot. An impression may also be the track or trail left by an animal.

Molds are formed when, say, a sea shell is buried and then the mud in which it is buried begins to solidify. If, at that time, the shell is dissolved by groundwater, then a mold of the shell is left in the rock (like the mold for a plaster of paris model). The mold can be found as is, or filled with more material; this filling is called a cast.

Those are three ways: mold, cast, and impression.

If wood, shell or bone is buried and groundwater of the right chemistry comes along, the bone or shell material can be altered to a material different from the original. This is called petrifaction.

Shells can also be buried and the material that makes them up can undergo a physico-chemical process called replacement. The original material is replaced, almost molecule by molecule, by a similar material, and sometimes the very fine structure of the shell or bone is left intact.

Finally, recrystallization occurs in shells that are buried. The original shell material recrystallizes, usually with the result that most of the fine structure is gone.

So..these are the types of fossils: cast, mold, impression or track, replacement, petrifaction, and recrystallization.

Answer 2

A fossil form when an organisem dead in a good site {a good site means that a place with high speed in precipitation} and dont decay or eat by other animals after along time this dead organism change to a rock that name it fossils

Answer 3

Je vais juste completer les autres reponses: Il ne faut pas oublier que toute forme de vie n'est qu'une forme qui reste dans le temps, donc un fossil c'est la volonte de la vie de rester inscrite tout le long des temps sous la forme qui lui a donné naissance.